[kesparate]

i'm having some trouble deep drilling some 2mm holes in a2. the cut begins at a depth of 1.2 inches and goes to 1.7 inches, to the start depth there is a 2.8mm hole. the trouble that i'm having is that the drills are just snapping off. i've run them at 1200rpm and a feed a 4., 2.5, and 1. inches per minute with a peck of .03, .015, and .001 respectively. i am using cobalt drills, some with and over all length of 2., and some that are oal of 4. i don't have anything in the middle.
any recommendations? thanks for helping.

[Mitsui Seiki]

If you have coolant through spindle,use a Regofix (or similar) ER collet chuck.
It makes a big difference.

[dertsap]

drill the 2 mm hole first , chances are the chips aren t coming out and are packing back into the hole

[kesparate]

coolant through spindle. that remains a dream. i've only got a 7k spindle...

dertsap. that's an interesting point. i was trying to minimize the amount drilled, but if the chips aren't clearing i'm shooting myself in the foot. how do i avoid huge wander in the drill if i have so much hanging out? perhaps .1" deep 2.8mm just to have something to follow.

[dertsap]

if you use a .03 peck and the proper speeds and feeds for the material your cutting ,then wander shouldn t be an issue

[roundman]

We found that at times the drills we used were very bent and so it obviously would break. We used coolant lines right on the drill and came out of the hole with each peck. Straight drills always do better.

[Caprirs]

1200rpm on a 2mm drill sounds pretty low to me even in A2. If you wanted to keep your SFPM down to 100, you'd need ~4700rpm. My opinion is you're not spinning the drill fast enough to help the chips up the flutes.

[kesparate]

i tried drilling the 2mm hole first and kicked the speed up a bit and got very good results. thanks for all your advise.
i would have gotten back sooner but while working on this problem some other job got much hotter, and it had top wait.

[Webderland]

also if your coolant goes bad and has a fowl smell it could be attributing to the problem

[big_mak]

A suggestion would also be to drill a 2mm started hole witha stub drill first, then go in with the longer drills. This will help get the holes in the right position